例句：
Be sure to give your family my regards.
務(wù)必代我向你的家人問好。
Even if you did see someone, you can't be sure it was him.
即使你確實看見有個人，也不能保證那就是他。
England must win this game to be sure of qualifying.
英格蘭隊必須拿下這場比賽才能確保獲得資格。
He is intelligent, to be sure, but he's also very lazy.
他固然聰明，但也很懶。
Whether or not we're successful, we can be sure that we did our best.
不管成功與否，我們確已盡了最大努力。